A variety of frostbite classification systems have been proposed. The easiest to understand, and perhaps the one that gives the best clues to outcome, divides frostbite into two main categories: 1) superficial and 2) deep.
In superficial frostbite, you may experience burning, numbness, tingling, itching, or cold sensations in the affected areas. The regions appear white and frozen, but if you press on them, they retain some resistance.
In deep frostbite, there is an initial decrease in sensation that is eventually completely lost. Swelling and blood-filled blisters are noted over white or yellowish skin that looks waxy and turns a purplish blue as it rewarms. The area is hard, has no resistance when pressed on, and may even appear blackened and dead.
The affected person will experience significant pain as the areas are rewarmed and blood flow reestablished. A dull continuous ache transforms into a throbbing sensation in 2 to 3 days. This may last weeks to months until final tissue separation is complete.
At first the areas may appear deceptively healthy. Most people do not arrive at the doctor with frozen, dead tissue. Only time can reveal the final amount of tissue damage.
There are milder conditions related to frostbite, including frostnip, chilblains, and trench foot.
Frostnip refers to the development of tingling sensations (paresthesias) that occur due to cold exposure. They disappear upon rewarming without any tissue damage.
Chilblain (or pernio) refers to a localized area of tissue inflammation that appears as swollen and reddish or purple. These develop in response to repeated exposure to damp, cold conditions above the freezing point. Chilblains may itch or be painful.
Trench foot was described in World War I as a result of repeated exposure to dampness and cold and exacerbated by tight boots. The affected feet are reddened, swollen, painful or numb, and may be covered with bleeding blisters. This condition is still observed in some homeless persons today.
Medically Reviewed by a Doctor on 1/30/2014
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